The present invention pertains to coupling assemblies for transmitting torque between machine elements having driving and driven components, and, more particularly, pertains to an inverted coupling assembly for providing power transmission between a power source, such as an electric motor, and driven elements, such as the gear pinion shaft for a gear box.
Couplings of numerous types and configurations are used for the transmission of torque between prime movers that can include gas turbines and electric motors and driven machinery and equipment such as pumps and gear reduction units. Since the driving and driven shafts may operate in harsh environments, under severe tensions and loads, and in low, intermediate, and high-speed applications, coupling assemblies for many specific applications have been devised.
For example, when the driven machine includes a thrust bearing, a slide-type coupling is usually employed that allows for axial movement of the driven shaft. Certain types of gas turbine machinery also use slide-type couplings for the shaft of the driven machine. In situations where thrust bearings are not used, a coupling that allows limited end float is instead used; and this type of coupling restricts the axial motion of the driven shaft.
Another type of widely used coupling includes a pair of gear hubs that are mounted on the driving and driven shafts and a pair of sleeves that mesh with the hubs. The sleeves mesh with the hubs through annular flanges that are bolted onto the sleeves. Because of the generally large external diameter of each hub and sleeve arrangement, this type of gear coupling requires applications where lateral space and centrifugal force are not critical limiting factors.
In a variation of the above-described coupling, a single cylindrical sleeve can be mounted in intermeshing arrangement on the hubs that are secured to the driving and driven shafts. However, this type of coupling has installation difficulties and also requires frequent servicing due to the reduced area of the lubricant channel.
For high-speed applications, a type of coupling is used that includes a flange mounted to the driving and driven shafts and a spacer disposed therebetween in driving engagement with the flanges by splines. This type of coupling does not allow for significant parallel offset and angular misalignment because the splines are not precision contoured.
A factor to consider in all coupling assemblies is the problems that result when drive elements are exposed to harsh and hazardous environmental conditions. In many applications the power source, such as the gas turbine or electric motor, is enclosed within a housing and fixedly mounted on bed or frame. The driven element, such as the pump or gearbox, is enclosed within an adjacent but separate housing, and on the same bed or frame in order to establish the operational spacing and relationships of the machinery. Nonetheless, portions of both the driving and driven shafts protrude unprotected from the respective housings; and the gear elements connecting the shafts are also fixed in position by the predetermined spacing. A hood or shroud can be used to enclose the driving and driven shafts, and the gear and coupling elements, but this causes numerous problems in the initial assembly and subsequent repair of all the aforedescribed machine elements.
For the specific application of power transmission between the electric motor and the gearbox pinion of electric motor driven mass transmit cars, gear couplings capable of high misalignment are typically used. Such gear couplings have crowned male gear teeth to allow the intermeshing engagement of the gear couplings to the motor shaft and gear pinion shaft. The sleeve gears of this type of coupling are provided with internal teeth that are normally flanged ring gears that are normally bolted together and the mounted on the hub gears. While this type of coupling arrangement allows the sleeve ring to float toward either the motor or gearbox, there is the possibility that the sleeve rings could contact the shroud or enclosure of the motor or gear box pinion thus damaging the machinery and necessitating costly repairs and downtime.
In view of the above problems and considerations, the prior art discloses a variety of coupling assemblies having wide-ranging industrial applications.
For example, Haworth et al. (U.S. Pat. No. 2,680,634) discloses an annular member, which provides a ball-and-socket connection between a stub shaft and a turbine shaft.
Morley (U.S. Pat. No. 2,706,125) discloses a shaft coupling that also provides an annular member for making a ball-and-socket connection among a compressor shaft, a stub shaft, and a turbine shaft so that thrust can be transmitted through the shafts.
Spier (U.S. Pat. No. 3,010,294) discloses a gear-type misalignment coupling that includes a misalignment coupling disposed between an input shaft and an output shaft, and at each end of the coupling a hub and sleeve arrangement is mounted for intermeshing engagement therewith in order to transmit power during various shaft misalignment configurations.
Hoffer (U.S. Pat. No. 3,132,494) discloses a flexible coupling for coupling a pair of rotatable shafts and accommodating a wider range of shaft misalignments and includes complementary pairs of hub and sleeve elements mountable to the ends of the respective shafts.
Kraeling (U.S. Pat. No. 3,243,973) discloses a flexible gear coupling for transmitting power between aligned and misaligned shafts and includes a hub and sleeve arrangement for mounting to the ends of the shafts so that each pair of hub and sleeve are in intermeshing engagement and each sleeve is capable of flexing within certain predetermined limits to facilitate load transmission between the shafts.
Heidrich (U.S. Pat. No. 3,521,462) discloses a gear coupling that includes a pair of externally toothed hubs fitted onto the ends of confronting shafts and which mesh with teeth of a sleeve interposed between the hubs. The sleeve includes longitudinal slots to provide for some limited torsional elasticity.
Shigeura (U.S. Pat. No. 3,613,395) discloses a shaft coupling device that includes a pair of internal and external gears mounted on the ends of opposing shafts and which are enclosed by a cylindrical housing. A resilient disc is disposed between the gear pairs for moderating vibrations and shocks that occur during operation of the machinery.
Pauli (U.S. Pat. No. 4,198,832) discloses a flexible drive coupling that includes a shroud for enclosing the driving and driven gear hubs. A flexible spacer member is disposed between the gear hubs to maintain proper spacing and alignment of the gear hubs.
Grant (U.S. Pat. No. 4,443,205) discloses a gear type shaft coupling that includes a pair of hubs and sleeves attached to the opposed ends of confronting shafts. Adjacent the inner end of each hub is a plate for stabilizing the shafts during operation.
Grant (U.S. Pat. No. 4,789,376) discloses a gear type shaft coupling that includes a hub and sleeve pair mounted on each end of confronting shafts and a ring that overlaps both hub and sleeve pairs and is fixed thereto for transmitting torque between the shafts.
Munyon (U.S. Pat. No. 5,393,267) discloses a coupling for driving and driven shafts that includes a pair of sleeves in the form of tubular members that can limit the end float of the coupling.
The present invention comprehends coupling assemblies for transmitting torque between the driving and driven shafts of an electric motor and gear box reduction unit, and, more particularly comprehends an inverted coupling for transmitting power between an electric motor and gear box pinion for a mass transit vehicle.
The present invention comprehends an inverted coupling for disposition between the motor and gearbox pinion and includes a shaft hub mounted on the motor shaft and a gearbox hub mounted on the gearbox shaft. The shaft hub and gearbox hub include annular splines or keyway configurations for accepting keys, corresponding splines or gear teeth. Both hubs are coaxially mounted with respect to the motor shaft and gearbox shaft. A pair of sleeve ring gears are mounted to the shaft hub and the gearbox shaft, and each sleeve ring gear is fixedly mounted to the respective shafts by internal ring gear splines that are radially arranged about the respective sleeve bores. Each sleeve ring gear includes an outer facing portion and a flange portion, and the flange portions extend toward one another when the sleeve ring gears are mounted on the shafts. The flange portions further define an interior annular sleeve surface, and mounted to each annular sleeve surface are a plurality of radially arranged ring gear teeth.
A pair of coupling members are interposed between the sleeve ring gears and partially overlap the shaft and gear box hubs and are themselves partially overlapped or encompassed by the flange portions of each sleeve ring gear. Each coupling member includes a plurality of inner male coupling teeth and a plurality of annular outer coupling teeth with the outer coupling teeth being disposed in intermeshing engagement with the ring gear teeth. Mounted circumjacent to the coupling members, and in driving engagement therewith, is a pair of center flanges. The center flanges are secured together in contiguous relationship and are connected to the inner male coupling teeth of the coupling members by internal radially arranged flange splines. Each center flange defines a center flange bore that is coaxial with the motor shaft and gearbox shaft. A pair of center plates are disposed within the center flange bores and are mounted to the coupling members for maintaining the alignment and positioning of the coupling members and relieving torsional stresses and loads that the elements of the inverted coupling may experience during the transmission of power between the motor shaft and the gear box shaft. Mounted to the interior annular sleeve surface of each sleeve ring gear, and outboard of the ring gear teeth, is a coupling member sleeve seal. The coupling member sleeve seals inwardly project toward the shafts in order to abut the respective coupling members thus forming an annular lubricant channel for holding and retaining therein lubricant.
It is an objective of the present invention to provide an inverted coupling having sleeve ring gears that are attachable to the driving and driven shafts by hubs in a configuration that avoids any interference with the shrouds, shields or enclosures for the motor and gearbox unit.
It is another objective of the present invention to provide an inverted coupling utilizing contact seals that position the sealing area for the lubricant in proximity to the centerline of the center flanges whose orientation is perpendicular to the axes of the driving and driven shafts.
It is still another objective of the present invention to provide an inverted coupling that allows for the replacement of the gear teeth elements of both the coupling members and the sleeve ring gears without causing damage to the shaft and gear box hubs and the center flanges.
It is yet another objective of the present invention to provide an inverted coupling wherein the expansion of the shaft and gear box hubs during assembly and operation causes the sleeve ring gears to be permanently fixed thereon so that rotatable motion of the sleeve ring gears independent of the hubs is prevented.
Yet another objective of the present invention is to provide an inverted coupling that allows changing of the coupling member sleeve seals or contact seals by removing the center flanges but without necessitating the removal of the sleeve ring gears.
Still another objective of the present invention is to provide an inverted coupling wherein the pitch diameter of the ring gear teeth and the outer coupling teeth are maximized to reduce the working stresses on the teeth and to provide for a larger lubricant channel.
Yet still another objective of the present invention is to provide an inverted coupling wherein the rotating mass mounted to the shaft hub and gear box hub is maximized while secondarily supported mass is minimized thereby resulting in enhanced balancing and loading of the elements of the inverted coupling.
Other and more specific advantages and objectives will become apparent from the specification that follows and from the drawings in which like numbers are used throughout to identify like parts.